Locking means for retractable aircraft landing gear



Dec- G. 1-1. DOWTY LOCKING MEANS FOR RETRACTABLE AIRCRAFT LANDING GEAR Filed June 22, 1937 2 Sheets-Sheet 1 7, 1937. s. HQDOWTY LOCKING Imus FOR RETRACTABLE AIRCRAFT LANDING GEAR Filed June 22, 191w ,2 Shets-Sheet 2 Patented Denim 1 937 Q t I,

@ 'UNlTED S'lATES PATENT OFFICE- LOCKING MEANS FOR, RETRACTABLE ama cam LANDING GEAR.

George Herbert Dowty, Cheltenham, England Application June 22, 1937, Serial No. 149,770 In Great Britain March 12, 1936 8 Claims. (01. 244-102) This invention relates to locking means for rewhich is slidable within a bore 23in the control tractable aircraft undercarriages andhas for an means it. The control lever i is formed with object to provide means which may prevent, or a recess 34, which when the control lever I5 is minimize the risk of, collapse of an underin a neutral position is in linewith the bore 23 5 carriage whilst an aeroplane is on the ground or so that movement of the locking plunger-:22, 5

partially or wholly ground-borne; causes said plunger to enter the recess 24 to pre- It has been found that with certain retraction vent operative movement of the control, lever l5. undercarriages and the aircraft standing on the Such movement of the locking plunger 23 is round, collapse has resulted either because of brought about by movement of'the lower part 9 some mistaken or mischievous operation, or by l2 of the leg ll into the upper part l3 of said 10 failure. The invention seeks to obviate such acleg, which latter movement is brought about by 'cidentsl At the same time the invention may be the weight of the aircraft when it is wholly or employed for the purpose of cutting on any elecpartially ground-borne. j tricai indication used in connection with the un- It will be seen that whenever the aircraft to dercarriage whereby consumption of current may which the above means are fitted is on the 5 be avoided, and possibly circuits not properly ground, itwill not be pwsible for anyone to re-, designed to be kept alive for prolonged periods, tract the undercarriage. r g i may be opened. In the arrangement shown in Figure 2, the The invention may be better understood by resilient telescopic leg 3| is held in the extended reference to the two preferred embodiments of position shown by means of a folding strut 32 it given by way of example and shown in the which is pivoted at one end at 33 to a fixed part accompanying drawings: t t of the aircraft, and at the other end at'34 to a Figure 1 shows in part sectional side elevation lug'on the unsprungor upper part 3|B of the an arrangement in which locking means serve to leg 3|. When the undercarriage is retracted the render inoperative-a control for the undercarstrut '32 folds about the pivots 33 and 34 and 2 riage;,and p f aboutthe pivot 35 intermediately of the length of 5 Figure 2 shows in sideelevation an arrangesaid strut 32. V In such an arrangement the fold ment in which locking means operate on the uning strut 32 is maintained in the position shown dercarriage structureitself. by means of a trigger member '38 pivoted at3l,

As shown in Figure 1, a shock absorbing reto one part of the strut 32, the trigger member sllient retractable leg, indicated generally at H, engaging with a pin 38 carried by a lug on the of an aircraft undercarriage has the lower or other part of said strut 32. The locking means, prung part l2, which carries the running wheel, comprises a, slidable rod 39 guided in lugs 40 on mounted to telescope against resilient means (not that part of the strut 32 to which the trigger shown) into the upper or unsprung part B3 of member is pivoted, the toggle members and 32, 35 said leg II. V i the member 82 ofwhich is in the form of a hell- It is well known that undercarriages may be crank lever. The toggle mem er M '15 pivoted, retracted hydraulically, and there is shown at" at43 to a lug on the sprung part 3IA of the leg H control means for bringing about the desired 3|, and the other member 42 is pivoted at 34,

retractive movements ofthe undercarriage, the independently of the strut 32, to the unsprung hand lever I5 serving to control a distributor part 3IB of the leg 3|, whilst the free end M of valve or operate a pump (not shown). The lower the bell-crank lever 42 abuts against the slidable and pper parts 12 and i 3 of the leg ll carry rod 39, which latteris spring-influenced to rehorizontal lugs l6 which are secured to the cormain in contact with the bell-crank lever. In

45 responding part of the leg by means'of clamping, the position shown in full lines, which is the 45 rings IL The lug B6 on the upper part l3 of the position itoccupies when the aircraft is air-borne,

leg serves as anabutment for one end of the the rod 33 is free from the trigger member 38,

outer casing M of a remote control mechanism, which latter is thus permitted to be rocked about the'other end. of which casingabu'ts against a its pivot 3'! to clear the pin 33 and permit the p cap l9 at the end of a tubular fitting 20 secured undercarriage to be retracted. The various parts to the underside of the control means M. The occupy the position shown in broken lines when lug Son the lower part l2 of the leg it serves the aircraft is ground-borne, the leg 31 having as an anchorage for a cable 2| of the' remote been contracted with consequent rocking movecontrol mechanism, the other end of the cable ment of the toggle members 4| and 42 about their having secured thereto a locking plunger 22 pivots 43 and 34, respectively. The rocking 55 movement of the bell-crank lever 42 causes the rod 39 to slide so that said rod 39 passes over the end of the trigger member 36 preventing it from being rocked clear of the pin 38 and thus preventing retraction of the undercarriage.

A red, such as that 39 of Figure 2, may abut at its end against the trigger member. In such a case the possibility of yielding in compression should be provided in the rod when the leg is under landing load compression greater than a normal static load. For example, the rod may be formed in sections capable of telescoping against strong compression springs.

It will be appreciated that a resilient tail wheel mounting may serve to operate locking means in accordance with the invention to bring about the desired locking of the undercarriage when the aircraft is on the ground.

If desired, the relative movement of the two parts of a resilient telescopic leg of an undercarriage may be utilized to open the electrical circuit of an indicator which when the aircraft is flying indicates the position of the retractable undercarriage, such opening of the circuit serving to prevent premature running down of the batteries.

What I claim is:--

1. In an aircraft undercarriage, retracting means for moving the undercarriage from an operative to an inoperative position, such undercarriage including yieldable shock-absorbing means under ground load, locking means to prevent operation of the retracting means, .and means operated by the ground load shock absorbing movement of the undercarriage to actuate the locking means.

2. In an aircraft undercarriage, retracting means for moving the undercarriage from an operative to an inoperative position, such undercarriage including shock-absorbing means yieldable under ground load, a member for controlling the retracting means, means for locking the member against movement to prevent operation of the retracting means, and a connection between the locking means and the undercarriage to move-the locking means into locking cooperation with the member under ground load yielding of the shock-absorbing means of the undercarriage.

3. In an aircraft undercarriage, retracting means for moving the undercarriage from an operative to an inoperative position, a member for controlling the retracting means, shockabsorbing means for the undercarriage yieldable under ground load, locking means to engage said member and hold the same against control movement of the retracting means, and a rod-like member connected at one end to that part of the undercarriage yieldable under ground load in the shock-absorbing function, the opposite end of the rod-like member being connected to the locking means whereby ground load yielding movement of the particular part of the undercarriage operates the rod-like member to move the locking means into locking cooperation with the control member for the retracting means.

'4. In an aircraft undercarriage, retracting means for moving the undercarriage from an operative to an inoperative position, a resilient telescopic leg forming part of the undercarriage structure and yielding under ground load, locking means for preventing operation of the retracting means, and a connection between said telescopic leg and said locking means to cause operative movement of the locking means incident to that movement of the telescopic leg resulting from ground load.

5. An aircraft undercarriage comprising retracting means for moving the undercarriage from an operative to an inoperative position, shock-absorbing means in the undercarriage permitting relative movement of a ground-engaging part of such undercarriage under ground load, a locking means serving when in operative position to lock the retracting means against retractive movement, and a connection operated by the element of the undercarriage movable under ground load to operate the locking means to maintain a locked relation of the retracting means.

6. An undercarriage for aircraft comprising shock-absorbing means including an element relatively movable under ground load, means for retracting the undercarriage from an operative to an inoperative position, a locking element operative to lock the retracting means against retracting movement, and a member associated in the ground load movement of the movable element of the undercarriage to hold the locking means in looking position.

7. An undercarriage for aircraft including a foldable strut for retracting the undercarriage from an operative to an inoperative position, a trigger member to interlock the parts of said strut against folding, the undercarriage including a member movable under ground load, and a rod connected to move with said member and provide when moved an abutment to prevent release of the trigger member.

8. An aircraft undercarriage including a part relatively movable under ground load, a foldable strut providing means for retracting the undercarriage from an operative to an inoperative position, a trigger movable to lock the parts of the strut against relative movement to thereby prevent retractive movement of the undercarriage, a rod normally free of the trigger and movable to a trigger-locking position to prevent release movement of the trigger. and a toggle lever controlling the rod and connected to and operated by the movable member of the undercarriage to move the rod in the ground load operation of the movable member into locking cooperation with the trigger.

GEORGE HERBERT DOWTY. 

